Wireless communication networks are increasingly being used for wireless communications with various types of wireless user equipment. The wireless network itself may include a plurality of wireless base stations, also commonly referred to as “base stations”, “radio access nodes”, “RAN nodes”, “NodeBs”, “eNodeBs” or simply as “nodes”, that define a plurality of cells, and a core network that controls the base stations and interfaces the base stations with other wired and/or wireless networks. The nodes may be terrestrial and/or space-based. The nodes communicate with wireless User Equipment (UE), also referred to as “user equipment”, “wireless terminals” or “mobile stations” or simply as “terminals”, using radio resources that are allocated to the wireless network. The radio resources may be defined in terms of time (for example, in a Time Division Multiple Access (TDMA) system), frequency (for example, in a Frequency Division Multiple Access (FDMA) system) and/or code (for example, in a Code Division Multiple Access (CDMA) system). The nodes may use licensed and/or unlicensed frequency spectrum. Radio resources may be assigned to UEs by the wireless network upon initial communication and may be reassigned due to, for example, movement of the UEs, changing bandwidth requirements, changing network traffic, etc.
Release 10 (Rel-10) of Long Term Evolution (LTE) wireless technology allows the aggregation of multiple carriers to send signals between a node and user equipment. The main carrier may be referred to as a primary carrier, while the additional carrier(s) may be referred to as secondary carrier(s). Also the terms Primary Cell (PCell) and Secondary Cell (SCell) are commonly used terminology to refer to primary carrier and secondary carrier, respectively. In Rel-10 of LTE, the secondary carrier is generally required to have features of a regular LTE carrier. That is, it carries synchronization signals over time and frequency synchronization, reference symbols for channel estimation and control signals for data allocations and other control functions much like the primary carrier.
The approaches described in this section could be pursued, but are not necessarily approaches that have been previously conceived or pursued. Therefore, unless otherwise indicated herein, the approaches described in this section are not prior art to claims in this application and any application claiming priority from this application, and are not admitted to be prior art by inclusion of this section.